This invention relates in general to a duplexing system and in particular to an improved apparatus combining copier, document feeder, copy sheet cleaning, and a sorter cooperating to produce duplex copies in collated order from precollated documents without rearranging the documents or copies. This application incorporates by reference U.S. Pat. No. 3,567,214 issued on Mar. 2, 1971, on a document feeder, U.S. Pat. No. 3,460,824, issued on Aug. 12, 1969 on a Sheet Sorter and U.S. Pat. No. 3,841,754 issued Oct. 15, 1974 to Edward E. Drexler et al. for a Duplex Reproduction System each being commonly assigned to the same assignee as the present application.
A variety of machines are known for creating copy xerographically on a commercial basis. For the most part, such machines in present commercial use are limited to making a limited number of reproductions from an original on one side. It is also known to produce two sided or duplex copies as described, for example, in U.S. Pat. No. 3,615,429. Recently, there has been a demand to produce duplex copies which can be sorted in collated stacks from a precollated order of documents fed to a platen in a minimum of time without rearranging or reshuffling of documents or copies by the machine operator.
A major problem with duplex report reproduction in some copiers has been toner deposition on the back (non-image) side of the copy during the simplex pass. This is usually caused by soiled transport belts and unfused toner particles. In any machine which uses a high thermal gradient fuser which fuses the toner on the imaged side copy sheets and does not fuse toner on the side of the copy sheet not being imaged (such as CHOW or flash fusers), the toner on the backside of the copy is not fused as the copy passes through the fuser and is easily brushed off the copy sheet. However, the marks on the side of the sheet being imaged are fused on the sheet and the copies are fed back through the machine in the duplex mode and similar (unfused) spots are deposited on the first (simplex) side of the copy. If the toner deposited on the blank side of the sheet during the first pass is not removed before duplexing, it will be fused onto the copy during the second pass, resulting in permanent degradation of copy guality.
Copiers in the past have employed cleaning devices but none have been used to clean the non-image side of copies after they have passed through the fusing station. For example, U.S. Pat. No. 3,679,302 to Frederic G. Ludwing discloses a copying system using two fusing steps and a brushing step with the latter being used to remove toner particles from the simplex side copy sheet after the first fusing step. Joseph Fantuzzo et al, U.S. Pat. No. 3,566,076 shows the use of a cleaning brush in a xerographic machine used to remove background from the simplex side of a copy after fusing has taken place. Shelffo et al in U.S. Pat. No. 3,387,586 and D. B. Granzow et al in U.S. Pat. No. 3,369,917 both disclose removing any iron filings that inadvertently may have become deposited on the back of sheets passing through a developer housing. A brush is shown in U.S. Pat. No. 3,682,738 issued to J. H. Smith, Aug. 8, 1972, used to shake loose powdered materials not adhered to a fabric to improve removal of the powdered material by a suction device.
Accordingly, it is an object of the present invention to improve copier/duplicator output.
Yet another object of this invention is to insure clean duplexed copies with consequently improved copy quality.
These and other objects of the instant invention are obtained generally speaking by employing a background cleanup or toner removal brush on the side of the copies not being imaged after the copy has passed through the fusing station and preferably after the last processor transport.